Under fire for dumping toxic pollution into Lake Michigan, owners of the last coal-powered steamship on the Great Lakes promised four years ago they would eliminate its murky discharges in time for the 2012 sailing season.

But with two weeks left before the Badger car ferry's season ends, they are seeking another reprieve that would allow the ship to keep churning coal ash into the lake every time it sails — 4 tons of waste concentrated with arsenic, lead, mercury and other heavy metals.

In documents filed with the U.S. Environmental Protection Agency, the owners are asking for five more years to fix the Badger's pollution problems. By 2017, they say, they can install new equipment that stores the coal ash onboard.

The owners suggest the 410-foot ship eventually might be fueled by cleaner-burning natural gas, though they acknowledge they might not be able to afford such an ambitious overhaul.

They also continue working in Washington to secure a permanent exemption from EPA oversight and protect the aging coal burner as a National Historic Landmark. If successful, the Eisenhower-era ship could pollute the lake indefinitely.

The latest moves to delay or thwart a cleanup of the Badger, backed by several elected officials in Wisconsin and Michigan, come as the EPA considers a new federal permit to replace one that expires Dec. 19. Wisconsin Gov. Scott Walker weighed in this month with a letter suggesting the EPA "temporarily extend" the Badger's current permit until officials find a solution "that keeps the ferry sailing and Lake Michigan better protected."

Built in 1953 to carry railroad cars, the Badger is billed today as a nostalgic vacation shortcut. Supporters have organized a public relations campaign that promotes the car ferry as an important part of the tourist economy in its port cities of Manitowoc, Wis., and Ludington, Mich.

After a Badger spokeswoman requested questions in writing from the Tribune, company officials did not respond. But in letters to public officials, the owners have said the ship's coal ash poses no threat to Lake Michigan.

They say that if the car ferry stops sailing, "thousands upon thousands" of vacationers could be forced to drive around the lake through Chicago traffic and harm the environment by increasing pollution from vehicle tailpipes.

"We ask these well-meaning people to balance the Badger's limited (environmental) impact with her economic and spiritual value and understand our long-term plan is to make the Badger the 'greenest' ship on the Great Lakes," the ship's owners wrote in an August letter to a Wisconsin state senator.

Coal ash pollution drew national attention in 2008 after a holding pond ruptured at a Kingston, Tenn., power plant. The EPA has proposed more stringent rules to ensure safe disposal of the waste, which the agency says poses "significant public health concerns."

Since the Badger's owners negotiated their 2008 deal with the EPA, the ferry has continued to dump about 509 tons of coal ash into Lake Michigan each year. During its spring-to-fall season, federal records show, the amount far exceeds the 89 tons of coal, limestone and iron waste that all other Great Lakes freighters combined discharge into the lake annually.

"There is no reason why this one vessel should be able to keep ignoring what every other ship on the Great Lakes did decades ago," said Joel Brammeier, president of the Alliance for the Great Lakes, a nonprofit environmental group.

Officials in the EPA's Chicago office said they are reviewing tests of the Badger's coal ash and other information submitted by the company and declined to comment until a draft permit is released for public review.

If the Badger wins another reprieve from the EPA, it will be its latest pass from environmental laws that other Great Lakes ships for years have complied with, including the Lake Express, a diesel-powered ferry that runs between Milwaukee and Muskegon, Mich.

Investors who saved the Badger from the scrap yard during the 1980s won special exemptions from Michigan and Wisconsin air quality laws that kept the ferry's thick black coal smoke legal. The current owners later rejected state aid to convert the Badger to diesel, telling the Ludington Daily News in 2001 they wanted to run the business "without governmental assistance."

More recently, after the owners failed to win a $14 million federal stimulus grant to convert the Badger to diesel, they shifted their efforts to blocking the EPA from enforcing a cleanup deadline. They have spent $290,000 on federal lobbyists since 2008, according to records compiled by the nonprofit Center for Responsive Politics.

In documents posted on the EPA's website, the Badger's owners say their preferred solution is converting the ferry to liquefied or compressed natural gas. The documents also show that such an overhaul would take years to complete and would first need to clear several safety, technical and financial hurdles.